cMUT devices and fabrication methods

• US 20050177045A1
• Filed: 02/07/2005
• Published: 08/11/2005
• Est. Priority Date: 02/06/2004
• Status: Abandoned Application

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Knight, Joshua Glenn, Degertekin, F. Levent, McLean, Jeffrey John
• Application Number:
  US11/053,672
• Publication Number:
  US 20050177045A1
• Time in Patent Office: Days
• US Class Current: 600/457
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type
• CPC Class Codes: G01N 29/2406 Electrostatic or capacitive probes, e.g. electret or cMUT-probes

Abstract

Fabrication methods for capacitive-micromachined ultrasound transducers (“cMUT”) and cMUT imaging array systems are provided. cMUT devices fabricated from low process temperatures are also provided. In an exemplary embodiment, a process temperature can be less than approximately 300 degrees Celsius. A cMUT fabrication method generally comprises depositing and patterning materials on a substrate (400). The substrate (400) can be silicon, transparent, other materials. In an exemplary embodiment, multiple metal layers (405, 410, 415) can be deposited and patterned onto the substrate (400); several membrane layers (420, 435, 445) can be deposited over the multiple metal layers (405, 410, 415); and additional metal layers (425, 430) can be disposed within the several membrane layers (420, 435, 445). The second metal layer (410) is preferably resistant to etchants used to etch the third metal layer (415) when forming a cavity (447). Other embodiments are also claimed and described.

Claims

1. A method of fabricating a cMUT on a substrate having a surface at a process temperature, the method comprising:

providing a first conductive layer proximate the surface of the substrate, the first conductive layer being resistant to an etchant;

providing a sacrificial layer proximate a portion of the first conductive layer; and

etching the cMUT with the etchant, wherein the etchant etches a portion of the sacrificial layer.

2. The method of claim 1, further comprising:

providing a first membrane layer proximate the sacrificial layer;

providing a second conductive layer proximate a portion of the first membrane layer; and

providing a second membrane layer proximate the second conductive layer.

3. The method of claim 1, wherein the process temperature is less than approximately 300 degrees Celsius.

4. The method of claim 1, wherein the substrate comprises an embedded circuit.

5. The method of claim 1, wherein the first conductive layer comprises Gold.

6. The method of claim 1, wherein the sacrificial layer comprises Chromium.

7. The method of claim 1, further comprising providing a transparent substrate as the substrate.

8. The method of claim 1, further comprising providing a reflective layer as at least one of the first conductive layer, the second conductive layer, the first membrane layer, and the second membrane layer.

9. The method of claim 1, further comprising providing a circuit proximate the substrate adapted to receive and provide optical signals.

10. A cMUT device comprising:

a first conductive layer of the cMUT device proximate a substrate, the first conductive layer being resistant to an etchant; and

a first membrane layer of the cMUT proximate the first conductive layer, the first membrane layer defining a cavity formed by etching a sacrificial layer with the etchant.

11. The device of claim 10 further comprising:

a second conductive layer proximate the first membrane layer; and

a second membrane layer proximate the second conductive layer.

12. The device of claim 10, further comprising a circuit proximate the substrate to direct and receive and at least one of an optical and electrical signal to and from the first conductive layer.

13. The device of claim 10, wherein the substrate enables at least one of an electrical or optical signal to pass through the substrate.

14. The device of claim 10, wherein the first conductive layer comprises Gold and the sacrificial layer comprises Chromium.

16. The device of claim 10, wherein the substrate comprises an embedded circuit.

15. The device of clam 10, wherein at least one of the first conductive layer is placed proximate the substrate at a temperature of less than approximately 300 degrees Celsius.

17. A method of fabricating a cMUT on a substrate having a surface, the method consisting of:

providing a first conductive layer proximate the surface of the substrate, the first conductive layer being resistant to an etchant;

providing a sacrificial layer proximate at least a portion of the first conductive layer;

providing a first membrane layer proximate the sacrificial layer;

providing a second conductive layer proximate at least a portion of the first membrane layer;

providing a second membrane layer proximate the second conductive layer; and

removing at least a portion of the sacrificial layer with the etchant.

18. The method of claim 17, further consisting of disposing an adhesion layer between the surface of the substrate and first conductive layer.

19. The method of claim 17, further comprising at least one of the first conductive layer, the second conductive layer, and the sacrificial layer at a temperature of less than 300 degrees Celsius.

20. The method of claim 17, wherein the substrate is adapted to enable at least one of an optical or electrical signal to pass through the substrate.